A coherence sweet spot with enhanced dipolar coupling

TL;DR

This paper introduces a singlet-triplet qubit in InAs nanowires that optimally balances strong coupling to control fields with minimal noise sensitivity, achieved through a specific magnetic field orientation.

Contribution

It demonstrates a new qubit design that maximizes dipolar coupling while minimizing decoherence, leveraging spin-orbit interaction in a novel material platform.

Findings

Maximal spin-photon coupling achieved at the sweet spot.

Decoherence minimized at the same sweet spot.

Theoretical analysis suggests phonons as the dominant noise source.

Abstract

Qubits require a compromise between operation speed and coherence. Here, we demonstrate a compromise-free singlet-triplet (ST) qubit, where the qubit couples maximally to the driving field while simultaneously coupling minimally to the dominant noise sources. The qubit is implemented in a crystal-phase defined double-quantum dot in an InAs nanowire. Using a superconducting resonator, we measure the spin-orbit interaction (SOI) gap, the spin-photon coupling strength and the qubit decoherence rate as a function of the in-plane magnetic-field orientation. We demonstrate a spin qubit sweet spot maximizing the dipolar coupling and simultaneously minimizing the decoherence. Our theoretical description postulates phonons as the most likely dominant noise source. The compromise-free sweet spot originates from the SOI suggesting that it is not restricted to this material platform, but might find applications in any material with SOI. These findings pave the way for enhanced engineering of these nanomaterials for next-generation qubit technologies.